1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method with which it is possible to perform predetermined processing such as cleaning upon semiconductor wafers, glass substrates for photo masks, glass substrates for liquid crystal displays, glass substrates for optical disk substrates and the like, and to a substrate position correcting apparatus for and a substrate position correcting method of correcting the positions of such substrates.
2. Description of the Related Art
While plural film forming steps to form thin films such as a photo resist on the front surface of a substrate such as a semiconductor wafer are among a series of steps to process the substrate, the film forming steps may result in formation of films also on the back surface of the substrate or in a rim portion of the front surface of the substrate. However, it is in general only an area where a device is to be formed at the center of the front surface of the substrate that demands film formation, and if film formation occurs on the back surface of the substrate or in the rim portion of the front surface of the substrate, the thin films formed on the back surface of the substrate or in the rim portion of the front surface of the substrate could fall off when contacting other apparatus at a step following the film formation steps, which could decrease the yield or lead to a trouble in a substrate processing apparatus itself.
Noting this, for removal of thin films formed on the back surface of a substrate and in a rim portion of the front surface of the substrate, the apparatus according to Japanese Patent Application Unexamined Publication No. 2000-235948 (Patent Literature 1) has been proposed for instance. In this apparatus, holding members such as chuck pins disposed in the vicinity of a rim portion of a base member hold a substrate whose surfaces bear thin films and the base member then rotates, thereby rotating the substrate. Further, a chemical solution is supplied to the back surface of the rotating substrate. At this stage, a rotating member whose opposed surface is opposed against the front surface of the substrate and which is spaced away by a predetermined distance from the front surface of the substrate rotates, the rotations of the substrate and the rotating member spread the chemical solution all over the back surface of the substrate, and the chemical solution etches away unwanted substances on the back surface of the substrate. The chemical solution also flows over to the rim portion of the front surface of the substrate via the edge surface of the substrate, and etches away unwanted substances which are in the rim portion of the front surface, too. In this manner, the thin films are etched away only on the back surface of the substrate and in the rim portion of the front surface of the substrate.
By the way, the substrate processing above is executed for removal of the thin films existing within a certain range which is from around a non-processing area approximately at the center of the front surface of the substrate, and it is desirable to accurately control this removal range, namely, the width that a film is removed from the substrate by the etching from the edge surface to inside (hereinafter referred to as the “rim etching width”. In the event that a metal layer of copper or the like is formed as a thin film on the front surface of the substrate in particular, it is extremely important to ensure a uniform rim etching width all along the circumference during the substrate processing above which aims at removal of metal in the vicinity of the edge surface (bevel).
It is therefore necessary to precisely align the physical center of the substrate (hereinafter referred to simply as “the center of the substrate”) with the center of rotations of the base member, such as a spin base, which rotates the substrate during the substrate processing above. The reason is because eccentricity (deviation) between the center of the substrate and the center of rotations of the base member results in variations of the amount of the chemical solution supplied to the rim portion of the front surface of the substrate and makes it impossible to ensure a uniform rim etching width all along the circumference of the substrate. This is similar also for such processing which requires supplying the chemical solution to the rim portion of the front surface of the substrate from a nozzle which is disposed facing the rim portion of the front surface of the rotating substrate for removal of a thin film formed in the rim portion of the front surface of the substrate. In this case, eccentricity between the center of the substrate and the center of rotations of the base member changes the distance between the edge surface of the substrate and the nozzle during rotations of the substrate, whereby the rim etching width becomes different along the circumferential direction. As a result, it is not possible to ensure a uniform rim etching width all along the circumference of the substrate.
Further, in the substrate processing apparatus for processing a substrate such as a semiconductor wafer described above, a transporter such as a transportation robot transports a substrate to be processed and hands the substrate over to a substrate rotator unit such as a spin chuck. However, eccentricity between the center of the substrate and the center of rotations of the substrate rotator unit invites inconvenience to the processing process as described above. Noting this, it is critical to reduce such eccentricity as much as possible.
Centering is therefore performed which aligns the center of the substrate to the center of rotations of the substrate rotator unit. In the apparatus described in Japanese Patent Application Unexamined Publication No. H7-7069 (Patent Literature 2) for example, a centering mechanism aligns the center of the substrate to the center of rotations of a suction stage (substrate rotator unit). More specifically, the centering mechanism closes, thereby holding a substrate at the outer rim of the substrate, and aligns the center of the substrate to the center of rotations of the substrate rotator unit. As the suction stage performs a sucking action, the substrate is fixed to a surface of the stage, which prevents deviation of the substrate.